1. Field of the Invention
The present invention relates to a power control system for a hot gas engine of the type in which the power output is controlled by varying the mean pressure of the working gas charge in the engine.
2. Description of the Prior Art
Power control systems for hot gas engines of the type referred to above will normally comprise a high pressure working gas reservoir a gas duct containing two series connected valves interconnecting said reservoir and the working gas chambers of a hot gas engine to be controlled and a gas compressor the suction side of which is connected to the working gas chambers of the engine via a duct containing a non-return valve and an on-off valve connected in series, the delivery side of said gas compressor being connected to said reservoir through a duct containing a non-return valve.
The British Patent Specification No. 1 383 860 shows an example of such known power control system.
However, in case of hot gas engines used for automobiles the maximum power output of the engine is many times greater than the minimum engine power consumption at idling. Therefore, the maximum working gas pressure is several times greater than the minimum working gas pressure. At idling and at low engine power outputs when the mean working gas pressure is low the compressor will have to operate under severe conditions--i.e. a great pressure difference between its suction and delivery side. It will generally be necessary to use a two-stage compressor if the compression ratio is greater than 8.